Homemade cake flour

I'm making a pound cake recipe that calls for 1 1/2 cups of cake flour. All I have at home is AP flour and tapioca starch. I really don't want to buy a whole bag of cake flour or corn starch even though I know I could make my own cake flour using some corn starch. The question is: can I make my own cake flour mix using some tapioca starch instead of corn starch?